The present invention relates to a vaporizer-pressure regulator for a combustion engine.
The invention is applicable to a combustion engine having an inlet duct including a gas or control valve where the vaporizer-pressure regulator has a first space divided into two compartments by a diaphragm located in said space, said diaphragm being provided for controlling a first closing valve cooperating with a gas feed orifice of the first space, while that compartment of the space in which the gas feed orifice opens out is connected by a connecting duct through a second gas feed orifice with a second space also divided into two compartments with the aid of a diaphragm, said second diaphragm serving to actuate a second closing valve cooperating with the second gas orifice and the space in which the connecting duct opens out is connected through a second connecting duct with the inlet duct of the engine.
In combustion engines and in particular in car combustion engines the fuel used is often formed by pressure-liquified, gaseous hydrocarbons such as LPG. The fuel is stored in the liquid state in a tank under excess pressure. The feed of the engine requires this liquid fuel to be gasified, after which the gas with air admixture in the inlet duct of the engine is fed to the engine. For this purpose a vaporizer-pressure regulator is used in which the pressure of the fuel is reduced and the fuel is converted from the liquid phase into the gaseous phase. This usually occurs in two stages, in which the first stage the fuel emanating from the tank is admitted in a first space through a gas feed orifice that can be opened and closed to a greater or lesser extent with the aid of a first closing valve, which valve is acted upon by a spring-loaded diaphragm arranged in the space.
The pressure in the tank may vary between 3 and 5 bars and in the first stage the pressure may be reduced to 0.5 bar. On the one hand there is a tendency to maximize the pressure reduction in the first stage in order to optimize the conversion of the fuel into the gaseous state, whereas on the other hand the pressure in the first stage must not become too low in order not to adversely affect the maximum capacity of the vaporizer-pressure regulator.
In the second stage the pressure is further reduced, to which end the gas is supplied from the aforesaid first space to a second space, the gas feed to said second space being usually controlled also with the aid of a closing valve actuated by a diaphragm.
According to the invention that compartment of the first space which is located on the side of the diaphragm controlling the first closing valve remote from said first closing valve is connected with the inlet duct of the combustion engine both downstream and upstream of the gas valve through ducts which include means capable of affecting the size of the passage of the ducts in dependence on the load of the combustion engine occurring during operation.
By using the construction embodying the invention, the position of the first closing valve can also be influenced in dependence on the pressure prevailing in the inlet duct of the combustion engine downstream and/or upstream of the gas valve in accordance with the load and the number of revolutions of the combustion engine. In practice it has been found that in this way an appreciable improvement in the operation of the combustion engine can be obtained.